Communication system



June 8, 1943. l w, M, BACON 2,320,997

COMMUNICATION SYSTEM Filed Aug. 17, 1940 5 Sheets-Sheet l TIME CON T ROLLED- 4 SECONDS.

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FIGURES IND CALL AC TI v4 TE GROUP i a a lNl/ENTOR Ni 5 WMBACO N N A T TOR/VEY June 8, 1943.

W. M. BACON COMMUNICATION SYSTEM Filed Aug. 17, 1940 5 Sheets-Sheet 2 POLAR/ZED OW OPE RA TE, 3 SECONDS.

FIGURES IND. CALL 4.9 o-

ROI/F lNl/EN TOR W M BACON A rick/My Jun'e s, 1943. w, M, BA N 2,320,997

COMMUNICATION SYSTEM Filed Aug 17, 1940 v 5 Sheets-Sheet s CALL & RECAL L AC T/VATE /Nl/E N TOR WM BACON l i I By 1111M.

ATTORNEY,

June 8, 1943.

W. M. BACON COMMUNICATION SYSTEM Filed Aug. 17, 1940 5 Sheets-Sheet 5 RECALL DISC.

CALL 8 RECALL CT/VATE IND, 0/5 C.

A TTORNEV Patented June 8, 1943 pairs CGMBEUNICATION SYSTEM Walter M. Bacon, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 1'7, 1940, Serial No. 353,086

12 Claims.

This application is a continuation in part of my application Serial No 290,743, filed August 18, 1939, and relates to communication systems and more particularly to telegraph systems wherein a. plurality of stations on a common channel may set up connections between each other and exclusively appropriate the channel to their own use.

The systems of this type of the prior art, such as disclosed in U. S. Patent 2,148,430, granted to Benjamin, February 28, 1939, are subject to false and improper operation due to extraneous and interfering currents. For example, if the line is momentarily opened due to some static Or other stray currents or interruptions of the circuit, the motors at all of the station will energize and continue to operate indefinitely, unless stopped by an attendant at some one of the stations.

It is an object of this invention to provide means for automatically stopping the motors at all of the stations if and when they may become accidentally or falsely started.

-An object of the invention is to provide automatic means for preventing unnecessary opera.- tion of stations on a party line when such stations are not involved in a connection. 'In particular, it is an object of the invention to prevent unnecessary operation of the motors of a plurality of teletypewriters connected to a party line. In accordance with this invention, and as a specific illustration of how the invention may be applied, a communication channel is provided to serve a plurality of stationseach equipped with a teletypewriter. A station circuit isprovided with means for sending out over the channel a prolonged signal of predetermined length for the purpose of calling in the other stations on the channel. By calling in is meant to change all the other stations from their normal nonoperative condition to an operative condition in which they are able to respond to the type of signal ordinarily used for their regular operation. Specifically, a time controlled switch is provided at each station for sending outover the common channel a spacing signal (Where the normal condition of the channel is marking) of the order of four seconds duration. Each other station on the channel will respond to such a signal by starting the teletypewriter motor thereat so that the mechanism of the teletypewriter will properly respond to permutation code signals.

According to the invention a slow-acting means or a timing meansis provided to maintainthis temporarily operative condition. Specifically, the motors of'all stations will be placed inoperation for a predetermined period of'sufiicient length for the subscriber who is establishing a connection to carry out other necessary operations. As illustrated, the motors of all other stations will run for about fifteen seconds and then if nothing else happens will automatically shut down. During this fifteen-second interval the calling station may put the other stations on the line on What may be termed a'conditionally permanent operative basis, that is, the fifteen-second timing means may be disabled so that at the end of the fifteen seconds if nothing else now happens themotors ofall stations will continue in operation. Thereafter the callin station may put selected ones of said other stations on what may be termed an unconditionally permanent operative basis, that is, such selected. stations are now placed beyond interference by any. furthe r operations at the calling station excepting, of course, thereleasing operation. Thereafter the calling station may release. those stations which are still on the conditionally permanent operativebasis and by so doing cause them to be locked out of the system and rendered incapable of interferin with the proper operation thereof. In one embodiment of the invention any one of the stations, party to an established connection, may be selectively disconnectedand such-station will thereafter :be locked out and rendered incapable of interference with the established connection. In one embodiment of the invention a locked out stationmay' be recalled and made a party to an established connection through operations carried out at any one of the stations, party to such established connection.

Each teletypewri-ter forming part ofthe circuit of the various stations is supplied with a number of contact sets operatedby the teletypewriter mechanism and in responseto various and particular codes. After the stations have been put on a temporary operative. basis by slowacting or timing means, the temporary basis is changed to a conditionally permanent.v basis through the operation of certain of-these contact sets at, eachstation by means of commoncodes. Thereafter individual stations, or a. group of such stations, are put on an unconditionally permanent basis by the operation f. certain other contact sets by codes individual-to such stations or individual to' aparticulang-roup of such stations.

particular station may be. equippedwith contactsets for individual calling, only or for group caningonly? or for both: Still other. contact sets may be provided for individual disconnect or roup disconnect.

At the calling statio means are provided to automatically place such station on a permanent rather than a temporary operation basis. This mean that the calling subscriber need only transmit the code for the particular wanted station or stations and need not transmit the code for his own station.

Any one or more of the stations on such a party line may be provided with tape transmitters. When the calling is started from an idle condition, the operation is the same as though the transmission were to be from an operators keyboard. However, a series of messages to different stations may be punched in the tape. At'the conclusion of one message the code combinations for figures and activate are followed by a common code combination which will operate a special contact set in the teletypewriter of all the stations which are so equipped. This will operate a slow-acting means which will not only send a prolonged calling-in signal over the line to return the selected stations not provided with a tape transmitter to normal and to unlock the non-selected stations, but will at the same time delay the further operation of the tape transmitter at the calling or transmitting station. This common code is then repeated to place all the other stations in a temporarily receptive condition so that by the further transmission from the punched tape, all the stations may be placed on a conditionally permanent operative basis, certain selected stations may be placed on an unconditionally permanent operative basis and the others locked out. Thus the code combinations for setting up a plurality of connections as well as the messages for each such connection may be punched in the tape and the sequentialoperation of setting up a connection, transmitting the message, releasing the connection, setting, up a new connection and so forth will be carried out automatically. Divisible subject-matter carved from this application is disclosed and claimed in application Serial No. 474,843, filed February 5, 1943.

Any one of the parties to the established connection may transmit and all will receive such transmitted messages,

Any one of the parties to the established connection may break down such connection and restore the channel to normal where it may be used by all the subscribers thereon.

- Other objects of the invention and features will appear as the description proceeds.

The drawings consist of five sheets each containing a circuit diagram and each illustrating a different form of the invention.

Fig. l is a circuit diagram showing a telegraph line i extending through a station represented by the rectangle 2, a station represented by the circuit diagram of the main part of Fig. 1 and other station represented by the rectangle 3. The stations 2 and 3 are the same as the Station shown in detail in Fig. 1. It will be understood that a suitable source of current and a return circuit are provided for the telegraph line which may contain a large number of stations, and that the normal condition is a closed circuit with current flowing in the line whereby the line relay 4 and the teletypewriter line relay 5 of each station are normally held to their marking contacts. Relay 4 is a neutral type relay, that is, it is biased so that when no current flows through its winding it moves its armature to its spacing contact.

It should be noted that relays 4 and 5 may be polarized relays in case polarized signals are transmitted over line I. In case so-called neutral signals, that is, signals of current and no current are transmitted over line I, relays 4 and 5 may be neutral relays or they may be polarized relays provided with a biasing winding and current 50 that they will respond to signal impulses of current and no current.

It is also within the scope of this invention to provide any suitable type of telegraph channel between the respective stations. This channel may include a full metallic telegraph line, a ground return telegraph line, a channel of the carrier telegraph system, a channel of a radio communication system, a telegraph channel of a composited telephone and telegraph line and may include both cable and open wire telegraph lines as well as a full duplex telegraph system or a channel of a multiplex telegraph system or any operable combination of these systems. The only essential is that at each of these stations the system responds to two signaling conditions of the line and that the communication system transmits to each station signals to which the two relays will respond.

When the operator at the station of Fig. 1 Wishes to call in some other station, he operates the time-controlled switch 6. This will open the line circuit for a period of four seconds and at the same time will cause the operation of relays 1 and i2. Relay 4 will move to its spacing contact, thereby energizing relay 8. Relay 8 is slow operating and is adjusted to move its armature only after being continuously energized for three seconds. Since the time-controlled switch causes the relay 4 to go to its spacing contact for four seconds, relay 8 will become energized.

Relay 8 controls a pair of relays 9 and l I which constitute a pair of counting relays well known in the art. These relays operate in one complete cycle for each two complete cycles of operation of relay 8. Thus, upon the first energization of relay 8, relay 9 becomes operated. When relay 8 becomes released at some later time, relay ll becomes energized. 7 When, subsequently, relay 8 again operates, relay 9 releases and when relay 8 again releases, relay ll releases.

Relay 9, therefore, now becomes operated and through its lower armature causes busy lamp l6 to light. Through this same connection a ground is placed on the inner armature of relay 1 to hold relays I and I2 locked.

During the operation of the time-controlled switch 6, relay I2 is operated and through its left-hand armature energizes relay l3 for closing the circuit of the teletypewriter motor M whereupon this motor starts into operation. I

At the end of four seconds, the time-controlled switch 6 again closes through the line and the relays 4 and 5 of the calling station as well as all the other stations on the circuit go to their marking contacts. The lower contact of the switch 6, which originally caused the energization of relay 1, is also opened but through the locking contact of relay 1 a ground is extended to the winding of relay I 2 so that this relay is maintained operated. As relay 4 moves to its marking contact, relay 8 is immediately released, with the result that relay ll becomes operated. Relay ll now establishes an alternate locking circuit for relays 1 and [2 through its lower outer armature,

at this station, the circuit will now remain in the condition just described with motor l4 running and-this condition would remain fixed indefinitely.

At all other stations on the line, such as the stations represented by the rectangles 2 and 3, the movement of the line relay 4 to its spacing contact in response to the operation of the timecontrolled switch 6 at the station making the call will result in the energization of relay 8 after the relay 4 has maintained its armature on its spacing contact for three seconds. Thereupon the relay 9 will become operated and cause the busy lamp Iii-to light. Thus, the busy lamps at all stations on the line become lighted. At these other stations relays I and I2 are not operated at this time. At the end of four seconds, the relay 8 at each of the stations releases, whereupon the relay H at such stations operates. Thereupon a circuit is established from ground, the contact and lower armature of relay 9, the inner lower armature and front contact of relay II, the winding of relay I0, the normal contacts of the left-hand armature of relay l2, the righthand armature and backcontact of relay ll, winding of relay I3 to battery. Relay l3 becomes immediately energized and starts the motor I 4 at each of these stations into operation. The relay ID, however, is slow to operate and must be energized in this circuit for at least fifteen seconds before it will operate. Thus, after the time-controlled switch 6 at the calling station completes its operation, there isa period of fifteen seconds during which the motors of all other stations on the line are operating and before which the relay I at each of these stations becomes energized.

If no other action is taken, then at the end of the fifteen seconds the relay It] becomes energized and causes the immediate release of relays 9 and II which in turn causes the release of relays It and I3 and the stopping. of the mo-. tor I4.

If within this fifteen-second interval the op-. erator at the calling station operates his transmitting contacts I8 to transmit the code for Figures, the contacts I9 at each station will be operated. Contacts [.9 are controlled by the platen member of the receiving device and are closed in response to the reception of a figure signal by the device. Contacts I9 when operated are closed so long as the device remains in the upper case. These contacts are open by sende ing an unshift or letter signal which returns. in mechanism to the lower case.

The other contacts 20, 2| and 22 are actuated only momentarily in response to the reception of the predesignated code combinations. These contacts close once for a short interval of time in response to the reception of each of the respective code combinations. For example, every time the activate code combination is transmitted contact 20 will momentarily close. The manner in which pairs of contacts such as I9, 20, 21 and 22 are operated is illustrated in Patent 2,120,235; granted to James F. Beattie et al June 14', 1938. If the calling operator again operatesthe transmitting contacts I8 within the fifteen-second interval to transmit a given code which will result operated. This results in the operation of relay 24 and relay 24.1ocks to the lower armature of relay II. The operation of relay 23 short-circuits relay I0 and prevents the stopping of motor I4 after the fifteen-second interval. Thus, all stations are now on a conditionally permanentinstead of a temporary operating basis.

The operator at the calling station now transmits another code which may be one arranged to operate the individual call contacts ZI of some particular station on the line, or it may be arranged to operate the group calling contacts of two or more particular stations on the line. There, of course, may be several such group calling contacts for calling different combinations of' stations, as indicated by the multiple conductors. In addition, the operator may transmit several of these calling code combinations each of whichoperates the individual contacts at different stations or each of which operates different group contacts at different groups of stations. Let it be assumed that the contacts 2| at the called station are closed. Thereupcn a circuit is established from ground, the outer right-hand armature and front contact of relay 23, contacts 2|, windings of relays 'I and [2, in parallel, to battery. Relay l2 thereupon substitutes an energizing circuit for relay I3 and opens the original circuit through the slow operating relay Ill. Relay I2 locks up through its outer righthand armature to the ground on the lower armature of relay II and relay Ill is short-circuited by the inner right-hand armature of relay 23. Thus, at the station or stations which have been called, the relay I2 is operated and such station or stations are put on an unconditionally permanent operative basis. Upon the operation of relay I2 a circuit is established through the inner right-hand armature of relay I2, the call bell 25, through the right-hand armature and contact of relay 26 to ground at the front contact and outer right-hand armature of relay 23. The operation of bell 25 notifies the attendant at the called station that his station is being called. He may stop the operation of this bell by momentarily depressing the key 21, which will cause the operation of relay 26 and which looks through its left-hand armature in order to maintain the circuit through its right-hand armature open.

The code for letters or space will now be sent to shut down the uncalled stations. This operation will cause the opening of the contacts I9 at all stations and the consequent release of relay 23. The release of relay 23 at the called stations interrupts the circuit of bell 25 and relay 26 and thus stops the operation of bell 25 if the attendant has not previously operated key 21. If the attendant has previously operated key 21, the release of relay 23 will release relay 26. The release of relay 23 at the called station also disconnects ground from the contacts 2! and 22 so that the subsequent operation of these contacts during the transmission of the following message will produce no effects upon the switching circuits or connections at any of the stations of the system.

All of the called stations are now in condition to communicate with each other for an indefinite period. Each one of the called as well as the calling stations may communicate or transmit to all of the other called or calling stations by operating a transmitting device having contacts IS. The line relays 4 and 5 at each of the stations follows the signals transmitted from the transmitting: station. Relay 5 causes the receiving teletypewriter or other receiving apparatus at each of the stations to record the message transmitted from the transmitting station. Relay 4 at each of these stations also responds to the signals transmitted over line I. However, during the normal transmission of signalsoveri line relay 4 will not continuously remain in a spacing position for three seconds. Consequently, relay 8 will not operate at any of the stations and thus will not interfere with the established connections.

At the uncalled stations, upon the first and operation of relay 23 the slow operating relay ID was short-circuited to prevent its operation and the consequent release of the counting relays 9 and H, the release of relay 23 at this time in response to the letters or space .code reestablishes the operating circuit through the slow operating relay I9. Relay I does not operate at once so relays 9 and II remain operated and relay 24 will be maintained locked operated. Therefore, a circuit is established from ground, the outer right-hand armature and back contact of relay 23, the left-hand armature and front contact of relay 24, the winding of relay H to battery through the back contact and inner right-hand armature of relay l2, resulting in the energization of relay H which in turn also opens the circuit of relay l3. Relay |3 releases and interrupts the operating circuit of motor M which motor stops at the uncalled stations. Relay H in operating interrupts the operating circuit of relay Ill before this relay operates so relays 9 and I remain operated at this time. Relay also establishes a shunting connection through the resistance 21 about the transmitting contacts I8, the teletypewriter line relay 5 and the time-controlled switch 6 at all stations which are not called or wanted in this connection. Thus, at such stations the teletypewriter is shut down, interference with the established connection is prevented, reproduction of the transmission at such stations is prevented and the relays 9, I I! and 24 thereat are maintained operative. The line relay 4 at such stations will operate in accordance with the code signals, but the relay 8, being arranged to respond only after being continuously energized for three seconds, will not operate. Interference with an established connection by a locked out station is prevented by a ground connection for the lower element of time-controlled switch 6 through a back contact on relay Since this relay is operated at all looked out stations the operation of switch 6 at those stations will be ineiiective.

At the end of the period of use any one of the stations effectively on the circuit may release the connection by operating its time-controlled switch 6 so as to cause the relay 4 at all stations to rest on its spacing contact for an equal length of time, that is, four seconds. Thereupon the relay 8 at the stations which have been locked out Will come up and this time release the relay 9 and as soon as relay 8 releases, the relay II will release, causing the relays l1 and 24 in turn to release and thus restore such stations to normal. The release of relays 9 and H at both the calling and called stations will also result in the release of relays l and I2 and consequently the return to normal will be complete at such stations.

Fig. 2 is a simplified arrangement of the circuit shown in Fig. 1. In this case, line 3| passes through stations 32 and 33 and the station represented by the circuit diagram of Fig. 2. Relay 34 is included in the line circuit and will remain on its marking contact or its spacing contact in accordance with the condition of the line, that is, whether it is closed or open. A time-controlled switch 36 and a set of transmitting contacts 31 are also included in the line. The teletypewriter selecting magnet 35 is connected to the marking contact of relay 34. t 1

With this arrangement an operator wishing to call another station on the line operates the time-control switch 36. The operation of the time-control switch 36 completes a circuit for the operation of relay 42 from positive battery through the winding of relay 42, lower contacts of switch 36 to ground through the lower inner break contacts of relay 4|. The operation of relay 42 also completes the circuit for operating relay 43 which in turn connects power to motor 44 thus conditioning the teletypewriter for operation at the calling station for operation. The operation of relay 42 also interrupts the shunt around the upper contacts of time-control switch 36, transmitting contacts 31, and break key 52.

The operation of the time-control switch 36 and the operation of relay 42 interrupts the line circuit 3|.

When line 3| is opened, relay 34 at all the stations of the system will operate the spacing contact and in three seconds cause the operation of relay 38. Relay 38 in operating completes a circuit for the operation of relay 39. At the end of approximately four seconds the upper contacts of switch 36 will close in line 3| and cause relays 34 at all of the stations to be operated to its marking position. Relay 38 at all stations on the line will then become deenergized which in turn results in the energization of the counting relay 4| thereat. The operation of relay 4| completes for maintaining relay 42 operated from positive battery through the winding of relay 42, the lefthand operated contacts of relay 42 to ground through the lower outer operated contacts of relay 4|. A circuit will also be established by the operation of relay 4| from ground through the lower inner armature and front contact of relay 4| and thence in one direction through the signal lamp 46 and in' another direction through the winding of relay 40, the normal contact and the right-hand armature of relay 45, winding of relay 43 to battery. Relay 43 becomes energized in series with relay 48 but relay 40 will not become energized for a period of fifteen seconds, so that if no other action is taken, the motor 44 will run for fifteen seconds whereupon the relay 49 will become operated and by releasing both relays 39 and. 4| will return the station to normal.

During this period of fifteen seconds the operator at the calling station will transmit the code for figures and then the code used to operate the activate contacts 48. With contacts 4! and 48 operated, relay 5| will become operated and looked through its left-hand armature and contacts 41, resulting in the operation of relay 45 and the substitution of a permanent energizing circuit for relay 43 and at the same time the disabling of relay 40 so that this relay cannot interfere with the condition of these stations. After the Figures and Activate codes have been sent, the individual call or the group call codes will be transmitted whereupon relay 42 at those stations called will operate. Relay 42 will then look to the lower armature of relay 39 and place 1all such called stations on a permanent operating asis.

At all other stations where neither, the individual call contacts 49 nor the group call contacts 50 have, been operated, therelay 42 will not be tion any one of the stations party to th connection may operate its time-controlled switch 36, with the result that the relays 33 of all stations on the line will be operated and then released, resulting in the release of relay 39 followed by the release of relay 4!, whereupon all stations are returned to normal condition.

Fig. 3 shows a third form of the invention wherein trigger tubes are used for slow-acting means rather than relays adjusted mechanically. In this figure the telegraph line BI passes through a number of similar stations two of which are illustrated by stations 62 and 63, represented by rectangles, and a third by the station shown in full in the diagram comprising the main part of Fig. 3. A line relay 64 is included in the line as well as a break key 6'! and a set of transmitting contacts Ill. The normal condition of the system is closed, with line relay 64 held on its marking contact. In this condition the controlling magnet 65 of the teletypewriter is held in a marking condition. At the station from which a call is established a key 66 is momentarily depressed. Thereupon a circuit is established from battery through the resistance 12, through the winding of relay 14, the contacts of key 66, the back contact and upper armature of relay 'II to ground. Relay I4 is energized in this circuit and thereafter its front contact and inner left-hand armare establishes a holding circuit independent of the key 66. The operation of relay I4 opens the line at its right-hand armature. By means of its outer left-hand armature, relay 14 at the same time removes a short circuit from about adjustable resistance 15 and fixed resistance 16.

Relay 68 is connected to the spacing contact of line relay 64 and when the line is opened by the right-hand armature of relay I6, the relay 64 moves to its spacing contact and causes the operation of relay 68. The operation of relay 68 establishes a circuit from battery through front contact and second outer right-hand armature of relay 68 through resistances I5, I6, TI and I8 in series to condenser 19 and thence to ground. By means of the adjustable resistances i5 and 18 this circuit is adjusted so that the condenser I9 will become charged sufficiently in a period of four seconds to cause the cold cathode tube 86 to flash over.

At all other stations on the circuit, except the calling station where relay I4 has been operated, the relay 68 will establish a circuit from battery through the front contact and second outer righthand armature of relay 68, the back contact and outer left-hand armature of relay I4, resistances TI and I8 in series to the condenser I9 and thence to ground. At these stations and with this lower resistance in series with the condenser I9, the condenser will become charged sufliciently to cause the cold cathode tube 86 to flash over in three seconds, thus reducing the time constant of the circuit by one second. The reason for the two times used is to give a good margin of'operation and to be sure that the circuit remains open long enough to operate the tubes at all stations. When the tubes flash over, continuous battery is placed on relay 69 in a circuit from battery through the front contact and second outer right-hand armature of relay 68 through the tube 86 to the winding of relay 69 and thence to ground. This current will continue to fiow until relay 68 releases. Therefore, relay 69 at all stations except the calling station will operate at the end of three seconds and this same relay at the calling station will operate at the end of four seconds.

The operation of relay 69 at all the stations placesground through its upper outer armature and front contact on the winding of relay H through the resistance SI and causes'the opera-- tion of relay II. This relay locks in an operated condition through the front contact and second upper armature of rela II.

At the calling station the initial operation of relay M has also placed ground on the winding of relay 62 through the front contact of the middle left-hand armature of relay I4 and second upper break contacts of relay 1 I. Relay 82 looks through its outer left-hand armature and front contact and second upper operated contacts of relay II after relay II has become operated. The operation of relay 82 causes the operation of relay '13 which causes the teletypewriter motor 83 at the calling station to startinto operation. The operation of relay 82 also removes a short circuit normally placed about the break key 61 and the transmitting contacts I0.

The operation of relay II at the calling station removes the original holding ground for relay I4 but this relay continues to hold up through the front contact and outer right-hand armature of relay 82 and the second outer upper operated contacts of relay 'II. The operation of relay II also places ground on its upper inner armature and front contact to cause the operation of busy lamp 84 and at the same time through the front contact and inner upper armature ofv relay 69 to the point between resistance I2 and the winding of relay 14, thereby short-circuiting relay I4 and causing it to release. The release of relay l closes the line at its right-hand armature and back contact and this results in the movement of all of the line relays 64 to their marking contacts. This in turn releases relay 68 at all stations, with the result that the battery circuit to the tube 86 is broken, and tube 86 extinguished and relay 69 released. The release of relay 68 completes a circuit for the operation of relay I63 from battery through the winding of relay I63, the right outer break contacts of relay 68 to ground through the uppermost operated contacts of relay H. Relay I63 in operating completes a circuit for maintaining itself operated from battery through its winding left-hand operated contacts to ground to the uppermost operated contacts of relay H. The operation of relay I63 removes ground from the upper terminal of condenser 88 and permits it to start to charge as described hereinafter.

The release of relay 66 at all stations establishes a connection from ground, the upper outer armature and back contact of relay 69 through the front contact and inner lower armature of relay II, the normal contacts of the inner righthand armature of relay to the winding of relay 73 which operates at all of the stations except the calling station. Relay [3 previously operated at the calling station asdescribed above. The operation of relay I3 at all these other stations now causes the respective motors 93 to start into operation.

At the same time that this is taking place, battery through the back contact and inner lower armature of relay 89 extending through the front contact and outer lower armature of relay 1 l, the middle right-hand armature and back contact of relay 85, adjustable resistance 85 and resistance 8! establishes a charging circuit for condenser 88. The resistances 86 and 81 are of the proper values to charge the condenser 88 sufiiciently to cause the cold cathode tube 89 to flash over in fifteen seconds. If at the end of fifteen seconds no change has taken place in the circuit, tube 89 will flash over, placing battery through the back contact and inner lower armature of relay 69, front contact and outer lower armature of relay "H, middle right-hand armature and back con tact of relay85, back contact and left-hand armature of relay 58, through elements of tube 89 to ground through relay I92 causing this relay to operate. Relay I82 in operating connects battery to the left-hand winding terminal of relay H thereby short-circuiting the relay H and causes it to release. However, if during the fifteen-second period the figures combination and the activate combination are transmitted by the transmitting contacts 19 at the calling station, the fifteen-second feature will be, stopped by the operation of relay 85.

Contacts 99 will respond to the reception of the figures code and contacts 9| will respond to the reception of the activate code whereupon relay 92 will become operated and will lock throughits left-hand armature directly to ground through the contacts 99. The operation of relay 92 results in the operation of relay 95 whereupon the original energizing circuit for relay 13 is broken and a substitute connection made through the inner.right-hand armature of relay 85 and the middle right-hand armature of relay 92 to ground".

The operation of relay 85 disconnects battery from the anode tube 89 and also from the charging resistance 86 thus preventing any further charge of condenser 88. The operation of relay 85 also provides a discharge path for condenser 88 fromthe upper terminal of condenser 88 through the left-hand outer operated contacts of relay 85 to ground through the middle set of break contacts of relay 68 thus discharging condenser 88 and preventing any discharge of tube 89 at thistime.

At the time that relay H operates, the busy lamp 84 at all stations lights as hereinbefore described, thereby indicating that the circuit is busy. The calling station now transmits the call combination for the stations desired on the circuit. This may take the form of an individual call which will operate the contacts 93 or a group calling combination which will operate the contacts 94. The operation, however, is the same for these two conditions. With either contacts 93 or 94 closed momentarily, a connection is established from ground, the front.

contact and outermost right-hand armature of relay 92, the contacts 93 or the contacts 94 to the winding of relay 82 so that this relay which has already been operated at the calling station will now become operated at the particular sta-.

tions called. Relay 82 at the called stations will look through the front contact and outer left-hand armature to a ground on the front contact and second upper outer armature of relay H. The operation of relay 82 also places ground on the winding of relay 13 to substitute for the connection hereinbefore established. The operation of relay 82 also removes the short circuits about the break key 51 and transmitting contacts 19 of those stations which have been called.

Following this, the sending of the code for letters or space will open the figures contacts 99, thereby removing the locking ground on relay 92, causing its release. Relay 85, however, will be maintained operated through its lefthand armature and front contact, the inner lower armature and front contact of relay H and the back contact and upper outer armature of relay 69. The release of relay 92 at the called stations will have no effect on the teletypewriter motors as these motors are now under the control of relay 82.

At the non-called stations, however, the release of relay 92 removes ground from the front contact of the middle right-hand armature, thereby releasing the relay 13 and stopping the motor 83. The control of the circuit has been removed from these non-called stations by the precedin operations. Since ground is no longer available at these stations through the call key 66 due to the operation of relay H and since relay H will remain operated throughout the ensuing period of communication, such nonealled stations will be unable to break in on the circuit. At the same time the break key 61 and the transmitting contacts 10 of these noncalled stations will remain shortcircuited through the right-hand armature and back contact of relay 82. Thus the non-called stations are locked out.

If it is desired to disconnect a station previously called, the figures and activate contacts 99 and 9| are operated through the sending of these codes at the previously called stations only. This is possible since the motors of the non-called stations have been shut down while the motors of the called stations are still in operation. The individual disconnect contact 95 is now operated through the sending of a particular code which is different for each station on the line. A group of stations may be disconnected by sending a group disconnect signal which will operate a contact similar to contact 95 at each station of the group. The operation of contact 95 extends ground from the front contact and outer righthand armature of relay 92 through contact 95 to the lower terminal of the winding of relay 82, thereby causing relay 82 to release. The release of this relay breaks the look through its outer left-hand armature, short-circuits the break key 6'! and transmitting contacts 19 and removes its control of the motor and control relay 13. When a letters or space signal is now sent, relay 92 releases through the opening of contacts 99 and removes the ground which during the operation of relay 92 was placed through the inner righthand armature of relay to cause the release of the motor control relay '13. The motor at the station to be disconnected now stops and the station is in the same condition as a noncalled station, described above.

To recall or add stations to the system the call and recall key 66 at any of the stations at this time connected to the line is operated. This operates relay 14 from ground through the middle left-hand armature of relay 82 and the contact of key 66 to the winding of relay 14. This opens the line for four seconds at the sending station as described in making a new call, and line relay 84 at all stations moves to its'spacing contact,

operating relay 68 as hereinbefore described. This starts the timingcircuit of tube -'80 as hereinbefore described. In this case again'at the end of three seconds at all the stations except the calling station and at the end of four seconds at the calling station relay 69 will operate. Relay 1|,however, is locked operated and the opening of the circuit from ground, upper outer armature and back contact of relay'69 removes ground over the circuit previously described to the winding of relay 85, causing the release of relay 85, The release of this relay starts the motors at-all of the stations previously out 01f the circuit as soon as relay 89 again releases at the end-of four seconds as previously described. This is done by placing ground through the upper outer armature and back contact of relay 89, the iront contact and inner lower armature of relay II, the normal contacts of the inner right-hand armature of relay 85 to the winding of relay 13. As previously described, the release of relay '69 at all of the stations starts the fifteen-second feature to operate. The circuit is now in the condition it was before the station selections were sent when a new call was being placed and the operation to select the added stations is the same as it was for adding new stations.

To return the circuit to normal or disconnect all the stations, the disconnect key 95 is operated at any of the stations on the circuit at the time. The operation of key 96 places ground used to operate relay I3 through the contacts of key 96 to the winding of relay 91 which now operates and locks through its inner left-hand armature and front contact. disconnect this also opens the line circuit at the right-hand armature and back contact of relay 9'! and at the outer left-hand armature and back contact of this relay removes a short circuit about theresistances I09 and IGI. The opening of the line releases the line relays at all the stations and operates relay 68 thereat. The operation of relay 68 places battery on the chargingcircuit of tube 89 and, as previously described, and at the end of three seconds this tube will fiash'over, operating relay 69 at all the stations. The operation of relay 69 places the battery through the front contact and second outer right-hand armature of relay 68, the front contact and lower outer armature of relay 59 on resistance 98 where-' upon current fiows through resistances 98 and 99 to condenser 88 at all the stations except the disconnecting station and through resistances 98, 99, I88 and IOI at the disconnecting station. These resistances are of such a value that when 98 and 99 are in the circuit alone, tube 89 will flash over at the end of six seconds and at the station doing the disconnecting where resistances I80 and IBI are also in the circuit the tube will flash over at the end of eight seconds. Battery is supplied to the anode of tube 99 through the left-hand armature and front contact of' relay 68. At the stations being disconnected at the end of six seconds when tube 89 flashes over, battery through the left-hand armature of relay 68 and through tube 89 is connected to relay I92. Relay I82 operates and in turn connects battery to the grounded side of the winding of relay II thereby releasing this relay which in turn releases relays 82 and 85, putting out the busy lamps and stopping the motors at these stations. At the station sending the disconnect, tube 89 flashes over at the end of eight seconds thereby dropping off its relays II, 82 and 85, turning off its motor, its busy lamp and at the same time At the station sending the removing the locking ground on relay 91, releasing this relay and closing the circuit through the right-hand armature and back contact of relay 91. This last circuit closed operates the line relay 84 at all stations, causing in turn the release of relay 68 and thereby breaking the battery circuits of tubes and 89, thus returning the circuit to normal condition.

In-order to eliminate the possibility of relay 68 following the teletypewriter signal which operates the line relay 64 and building up a charge in the timing circuits of tubes 89 and 89, the back contacts of the middle and inner right-hand armatures of relay 88 place a ground on the battery side of the charging condensers I9 and 88 each time relay 68 releases thereby discharging the condensers and only permitting tubes to operate when relay 88 remains operated for the required periods of 3, 4, 6 or 8 seconds as hereinbefore described. The circuit from ground through the outer right-hand armature and front contact of relay 85 which would normally discharge the condenser 88 is broken by the relay 68 so that the fifteen-second feature will operate when relay 85 is released.

Fig. 4 is a modification of the arrangement shown in Fig. 1. In this case the station shown in detail is equipped with a tape transmitter such, for instance, as that described in the patent to E. F. Watson No. 2,055,567 granted September 29, 1936. Any number of the stations of the system may be so equipped but it is not necessary that they be all so equipped. If the line is idle the operation is the same as that described in connection with Fig. 1 except that the figures combination for operating contact I9, the activate combination for operating contact 29, the individual call combination for operating contact 2| -or the group call combination for operating contact 22 and the letters combination for locking out the non-select stations may be all punched in the tape and transmitted therefrom. The select'ion is started by the operation of the control switch 5. The operation of the time control switch 8 causes the motors I4 to start on the temporary basis as described above. After four seconds switch 5 will close line I, thereafter the operator or attendant atthe calling station will close switch I06 which closes the circuit of the start magnet of the tape transmitter. transmitter will then transmit the signals perforatedin the tape. Under these circumstances the first signals perforated in the tape should be a figures code followed by an activate signal and then the signals representing the stations it is desired to call, followed by the letters or space signal which will lock out the other stations connected to the system. Thereafter the message will be transmitted from the tape controlled transmitter in accordance with the perforations in the tape.

If it is desired to connect additional stations or a new group of stations this may be accomplished without releasing the connection and starting over manually in the following manner: The figures combination and the activate combination are punched in the tape after the conclusion of the message punched in the tape for the previously established connection. These combinations transmitted will operate relay 23 as before described. A common recall combination is then punched in the tape which, when transmitted, will result in the operation of contacts I04. The operation of these contacts at all the stations provided with these contacts including The tape tion of the time-controlled switch 6.

the station where the selecting is taking place places ground through the front contact and the outer right-hand armature of relay 23, contact I04, winding of relay I02 to battery, resulting in the operation of relay I02. This relay locks through its front contact and inner lower armature to the armature and back contact of relay I03. Relay I03 is now energized in a circuit including the outer lower armature and front contact of relay I02. Relay I03, however, is slow to operate and will not move its armature for at least four seconds. Therefore, relay I02 is maintained in operation for this period of time. At the end of about four seconds relay I03 operates and releases relay I02 which relay then releases relay I03.

The operation of relay I02 opens the line at the outer upper armature of relay I02 so as to provide the same sort of operation as theopera- This foursecond open interval has therefore been sent over the circuit and has resulted in the operation and release of relay 8 which causes the release of relays 9, II, and I1 at all the stations not previously selected and also those stations previously selected which are not equipped with tape transmitters and contacts I04. The selecting and previously selected stations which are equipped with contacts I04 have not been affected since the operation of relay I02 has by its innermost upper armature opened the circuit between the armature of relay 8 and the circuit of the conuting relays 9 and I I. Thus the stations previously selected remain in operative condition.

At the selecting station relay I02 through its middle upper armature and back contact opens the circuit to the start magnet I of the tape transmitter so as to prevent further transmission from the tape during this four-second period.

Several blank code combinations will be punched in the tape following the first common recall combination. A considerable period of time may elapse from the time of the transmission of the first common recall combination punched in the tape until contacts I04 and relay I02 operate to stop the tape transmitter. During this time at least a portion of the following code combination recorded in the tape will be transmitted by the tape transmitter. Consequently, it is necessary to record certain code combinations in the tape a portion of which may be transmitted during the operation of relay I02 and which will not materially interfere with the operation of the switching equipment on any of the stations. Any suitable spare or unused code combinations may be used for this purpose. In the preferred embodiment of this invention a blank code combination is employed. By a blank code combination is meant a code combination in which all of the impulses are spacing and represented by no current in the line combination.

A second common recall combination then punched in the tape will result in a second closure of contacts I04, the operation and release of relays I02 and I03 and the second opening of the line for four seconds resulting in the starting of the motors of all of the stations which were not running prior thereto. Since all stations are now prepared for the reception of the figures, activate and the series of selecting combinations, such combinations punched in the tape will result in the selection of wanted stations as hereinbefore described.

Following the second common recall combination several more blank code combinations will be perforated in the tape controlling the transmitter to insure the proper operation of the switching circuits and the tape transmitter.

In Fig. 4 the transmitting contacts I8 represent the transmitting contacts of the teletypewriter and are controlled by the teletypewriter keyboard. The tape transmitter contacts are illustrated by contacts I09. These contacts transmit signals in accordance with punches in a tape as described in the above-identified patent to Watson.

Fig. 5 is a modification of the arrangement shown in Fig. 3. Where the operation of this circuit is desired from a punched tape, two additional code combination operated contacts I01 and. I08 are provided. After the system has been started by pressing the call key 06 the transmitter-distributor switch I06 is operated at the station sending the selection. The selections are then sent over the line from the transmitterdistributor as soon as the relay 14 has released and closed the circuit of the start magnet I05 through the inner right-hand armature and back contact of relay 14 and the inner right-hand armature and back contact of relay 91. As in the system shown in Fig. 4 blank code combinations are perforated in the tape preceding the switching code combinations as well as following a re- ;call signal to insure the proper operation of the system. To recall any station or stations or disconnect the system from a punched tape a recall or disconnect combination is punched in the tape to operate either contact I01 or contact I08 after the contacts 90 and 9| have been operated. The operation of contacts 90 and 9| operates relay 92 as hereinbefore described and places ground from the contact and outer right-hand armature v of relay 92 through the left-hand element of the switch I06 to the contacts I01 and I03. When either of these contacts then operates, it places ground in the one case over contact I01 to the winding of relay 14 for a recall and in the other case through contact I08 to the winding of relay 91 for a disconnect and the operation of these relays manipulates the circuit as before described. At the same time the circuit of the transmitterdistributor start magnet I05 is opened by the operation of either relay 14 or relay 91 so as to stop the feeding of further tape until the circuit is prepared to receive selecting or disconnecting combinations.

What is claimed is:

1. In a communication system, a station circuit, means responsive to a signal of a predetermined time interval for conditioning said station circuit for reception, means for holding said station circuit in said condition for a second predetermined period of time and for then automatically releasing said circuit, and means operative within said second predetermined period for disabling said automatic releasing means.

2. In a communication system, a station circuit normally in non-operative condition, slowoperating means responsive to a prolonged signal for putting said station circuit in operative condition, time-controlled means for automatically returning said station circuit to its said normal condition, and permutation code responsive means for rendering said automatic means inoperative.

3. In a communication system, a communication channel including in series a plurality of station circuits, each of said station circuits including time-controlled means for sending a prolonged signal over said channel to all of said station circuits included therein, means in each station circuit responsive to said signal for rendering said circuit operative, automatic means for returning each said station circuit to its normal non-operative condition after a predetermined time, means at each said station circuit responsive to a permutation code signal for disabling said automatic means, and additional means at each said station circuit responsive to a different permutation code signal for locking said station circuits in an operative condition,

4. In a communication system, a communication channel including in series a plurality of normally non-operative station circuits each including time-controlled means for sending a prolonged signal over said channel, slow-acting means in each station circuit responsive to said signal for placing said station circuit temporarily in operative condition, means in each said station circuit responsive to a common permutation code signal for placing said station circuit permanently in operative condition, means in each said station circuit responsive to a different permutation code signal for locking said station circuit against interference by further permutation code signals, and means in each said station circuit responsive to another common permutation code signal for selectively returning any operative station circuit to normal condition.

5. In a communication system, a communication channel including a plurality of station circuits, means at each station for calling one or more of the remaining stations on said channel, said means comprising means responsive to a prolonged signal for bringing all said remaining stations into a temporarily receptive condition for a limited period of time only, means operative within said temporary period responsive to a common particular normal length signal for placing all said remaining stations in a permanently receptive condition, means thereafter responsive to individual particular normal length signals for placing corresponding individual ones of said remaining stations in a receptive condition beyond interference by further normal length signals, and means thereafter responsive to a common particular normal length signal for returning all stations not placed in said last-described condition to normal and for locking such returned to normal stations effectively out of said communication channel.

6. In a communication system, a communication channel including a plurality of stations each having means to communicate with the other stations on said channel by signals of a given length, means at each station for transmitting over said channel signals of abnormal length, means comprising trigger tubes in resistance and condenser controlled circuits for timing said abnormal length signals, means responsive at all the remaining stations on said channel for bringing each of said stations from a normally nonreceptive condition to a condition temporarily receptive to normal length signals, means comprising trigger tubes in resistance and condensercontrolled circuits for timing said temporary periods, and means responsive to coded normal length signals for disabling said last timing means.

'7. In a communication system, a communication channel including a plurality of station circuits normally in a non-receptive condition and each provided with means to communicate with the others by signals of a given length, means at each station for transmitting over said, channel signals of abnormal length, means at each station responsive to abnormal length signals for temporarily placing said stations in a receptive condition, means thereafter responsive to common coded signals of said given length for placing said station on a conditionally permanent receptive condition, means thereafter responsive to individual coded signals of said given length for placing said stations on an unconditionally permanent receptive condition, means thereafter responsive to common coded signals of said given length for returning non-selected stations to their normal non-receptive condition, means thereafter responsive to individual coded signals for returning selected stations to their normal nonreceptive condition, and means thereafter responsive to said abnormal length signaling means at any one station now in a receptive condition for returning said channel and all stations thereon to normal.

In a communication system, a communication channel including a plurality of teletypewriter stations each equipped with a teletypewriter having a plurality of contact sets operated by the permutation code operated mechanism of said teletypewriters, means for calling said stations in for a temporary and predetermined period, and means including said contact sets for placing all stations on a conditionally permanent operative basis, apparatus for selecting particular stations and placing such selected stations on an unconditionally permanent basis and means for looking out all stations not selected.

9. In a communication system, a communication channel including a. plurality of teletypewriter stations each equipped with a plurality of contact sets operated by the permutation code operated mechanism of said teletypewriters, tape transmitting means at certain of said stations, means for calling said stations in for a temporary and predetermined period, means including said contact sets for placing all stations on a conditionally permanent operative basis, instrumentalities for selecting particular stations and placing such selected stations on an unconditionally permanent basis and means for looking out all stations not selected and additional means at said stations including tape transmitters for delaying the movement of the tape during the operation of calling in said station for a temporary and predetermined period.

19. In a communication system, the method of communicating over a channel including a plurality of teletypewriter stations at least one of which is provided with a tape transmitter which consists in first transmitting a prolonged callingin signal to place all other stations on a temporarily receptive basis and then within said temporary period transmitting permutation code signals for causing the following steps to be taken, which are (1) placing all other stations on a conditionally permanent operative basis, (2) selecting one or more stations for message reception and placing such selected stations on an unconditionally permanent operative basis, (3) looking out of non-selected stations, (4) transmission by sending station and reception by selected stations of message, (5) placing sending station on a conditionally permanent operative basis, (6) releasing selected stations, unlocking non-selected stations and returning such stations to normal and at the same time delaying the action of the operating tape transmitter.

11. In a telegraph system, telegraphic apparatus including a motor, means for starting the motor from a remote point, apparatus for causing the motor to operate for only a temporary time interval of a definite, fixed, and predetermined duration, and apparatus selectively controllable by code combinations within said temporary time interval for continuing the operation of said motor for a further time.

12. The method of remote control of a station having telegraph apparatus including a driving motor, a line extending to said station and operatively interrelated to said apparatus which comprises starting the motor by remote control over said line and selectively either continuing the operation of the motor by impressing upon said line a special sequence of code conditions or stopping the motor after the absence of said special sequence during a predetermined interval of time.

WALTER M. BACON. 

